The objectives of this research program are an analysis of the roles of chemical carcinogen in the induction and expression of preneoplastic and neoplastic murine mammary lesions. Specifically, the neoplastic potentials and biological properties of ductal hyperplasias as well as typical alveolar hyperplasias occurring in carcinogen-treated mice are being examined under a variety of conditions. Additionally, the endocrine changes occurring in carcinogen-treated mice are being correlated with the endocrine responsiveness of mammary preneoplastic lesions to determine the significance of endocrine changes in relation to the preneoplastic and neoplastic transformation as it occurs in the mouse mammary gland.